How to find specific entry values in a vector?

I would like to consider only the 3's between the 1's and 2's.

x = [1, 1, 1, 3, 3 ,3 ,2 ,2, 3, 3, 1, 1, 1 , 3, 3, 2 ,3,...];

Desired result: r = [0, 0, 0, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 ,3 ,3 , 0 ,....]

for i = 1:length(x)-1

if x(i)==1 && x(i+1) == 3

while ...?

Answer 1

[KSSV]

x = [1,  1,  1,  3,  3  ,3  ,2  ,2,  3,  3,  1,  1,  1  , 3, 3, 2 ,3];
x(x~=3) = 0

x = 1×17

0 0 0 3 3 3 0 0 3 3 0 0 0 3 3 0 3

[LS]

Thanks, but it's not what I meant. I would like to get these values (every group of 3's between 1 and 2)